For anybody thinking about making birdmouth paddle shafts, Lee Valley has just simplified the process by adding router bits to their catalog. A more complete description of the process is found on Shawn Baker's website. for making a paddle, 6 of the sides are small (e.g. 3/8" wide), 2 are wide (e.g. 5/8"), and are arranged 3 short / 1 long / 3 short / 1 long. The ridges are then planed or sanded down and the result is a light, stout shaft with lots of glue area between the strips.

The cuts can also be made on a table saw with an adjustable arbor angle, but it's difficult to match the precision of a router table with one of these dudes in it.